IDUs occupy a central position in the HIV epidemic; they are the second leading risk group and the principal source for heterosexual transmission of the disease in the United States. Among females, drug injection plays an even more significant role as it is their greatest risk factor, followed by heterosexual contact with an infected male. One-third of out-of- treatment IDU's interviewed in Denver from 1992-1993 reported injecting with a needle that they knew had previously been used by another IDU without disinfecting it first. Moreover, relapse to high-risk behaviors is common among those who initiate risk reduction. These findings call for the development and study of interventions that go beyond encouraging safer drug use. We are responding to this need by proposing a controlled test of a manual driven intervention that integrates street outreach by community coworkers and formal substance abuse treatment services. It is a prospective study, with a two-by-two factorial design and random assignment of 880 IDUs to one of four conditions; 1) a street-based, individual risk assessment (IRA) intervention conducted by community outreach workers teaching safer drug and sex practices; 2) the same IRA intervention but with the addition of free substance abuse treatment for 90 days (IRA-T); 3) an enhanced individual risk assessment (EIRA) intervention, in which community outreach workers initially provide the IRA intervention but then perform in a role-induction capacity, using motivational interviewing techniques and following the stages of change model, in order to encourage and facilitate treatment entry and, subsequently, reinforce clients' decision to remain in treatment; or 4) the EIRA intervention with 90 days of free substance treatment (EIRA-T). It is hypothesized that treatment entry, treatment compliance, and treatment retention will be significantly greater among subjects assigned to the EIRA, as well as to free treatment interventions, compared to the IRA and non-free treatment interventions. Lower frequencies of drug use, reflected tin self-reports and verified through urinalysis, and greater HIV risk-reduction, will significantly favor subjects assigned to the EIRA interventions compared tot he IRA interventions, as well as subjects assigned to free treatment compared to non-free treatment. The stages of change model will be used to measure readiness for change and as an outcome measure to evaluate the effectiveness of the four interventions in modifying specific drug-related behaviors. Using this model, subjects assigned to the EIRA interventions will show more progressive movement then will subjects assigned to the IRA interventions. Perceived self-efficacy will also reflect greater improvement by EIRA subjects than by IRA subjects, and perceived self-efficacy will be significantly associated with behavior change. It is also hypothesized that the EIRA-T intervention will be more cost-beneficial than will either of the IRA interventions. The study will be evaluated using formative and summative methodologies with emphasis on assessing intervention dose response and its relation to outcomes.